Catheter with multiple microfabricated temperature sensors

ABSTRACT

A catheter with temperature sensing has a catheter body and a tip section with integrated thermoresistive temperature sensors on its outer surface. The temperature sensor includes a microfabricated thin film assembly of which one layer is a sensor layer of thermoresistive material. In one embodiment, the tip section has a flexible tubing on whose outer surface circumferential temperature sensors are integrated. In another embodiment, the tip section has a tip electrode on whose outer surface a tip temperature sensor is integrated. In yet another embodiment, the tip section has a tip temperature sensor integrated on its tip electrode and multiple circumferential temperature sensors distal of the tip temperature sensor.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority of U.S. Provisional Patent ApplicationNo. 60/628,442, filed Nov. 15, 2004.

FIELD OF THE INVENTION

The present invention relates to a catheter having a temperature sensor,in particular, a catheter with multiple microfabricated temperaturesensor integrated thereon to provide interfacial temperature measurementat or near a distal tip.

BACKGROUND OF THE INVENTION

Electrode catheters have been in common use in medical practice for manyyears. They are used to stimulate and map electrical activity in theheart and to ablate sites of aberrant electrical activity.

In use, the electrode catheter is inserted into a major vein or artery,e.g., femoral artery, and then guided into the chamber of the heartwhich is of concern. Within the heart, the ability to control the exactposition and orientation of the catheter tip is critical and largelydetermines how useful the catheter is.

In certain applications, it is desirable to have the ability to injectand/or withdraw fluid through the catheter. This is accomplished bymeans of an irrigated tip catheter. One such application is a cardiacablation procedure for creating lesions which interrupt errantelectrical pathways in the heart.

A typical ablation procedure involves the insertion of a catheter havinga tip electrode at its distal end into a heart chamber. A referenceelectrode is provided, generally taped to the skin of the patient. RF(radio frequency) current is applied to the tip electrode, and currentflows through the media that surrounds it, i.e., blood and tissue,toward the reference electrode. The distribution of current depends onthe amount of electrode surface in contact with the tissue as comparedto blood, which has a higher conductivity than the tissue. Heating ofthe tissue occurs due to its electrical resistance. The tissue is heatedsufficiently to cause cellular destruction in the cardiac tissueresulting in formation of a lesion within the cardiac tissue which iselectrically non-conductive. During this process, heating of theelectrode also occurs as a result of conduction from the heated tissueto the electrode itself. If the electrode temperature becomessufficiently high, possibly above 60.degree. C., a thin transparentcoating of dehydrated blood protein can form on the surface of theelectrode. If the temperature continues to rise, this dehydrated layercan become progressively thicker resulting in blood coagulation on theelectrode surface. Because dehydrated biological material has a higherelectrical resistance than endocardial tissue, impedance to the flow ofelectrical energy into the tissue also increases. If the impedanceincreases sufficiently, an impedance rise occurs and the catheter mustbe removed from the body and the tip electrode cleaned.

In a typical application of RF current to the endocardium, circulatingblood provides some cooling of the ablation electrode. However, there istypically a stagnant area between the electrode and tissue which issusceptible to the formation of dehydrated proteins and coagulum. Aspower and/or ablation time increases, the likelihood of an impedancerise also increases. As a result of this process, there has been anatural upper bound on the amount of energy which can be delivered tocardiac tissue and therefore the size of RF lesions. Historically, RFlesions have been hemispherical in shape with maximum lesion dimensionsof approximately 6 mm in diameter and 3 to 5 mm in depth.

In clinical practice, it is desirable to reduce or eliminate impedancerises and, for certain cardiac arrhythmias, to create larger lesions.One method for accomplishing this is to monitor the temperature of theablation electrode and to control the RF current delivered to theablation electrode based on this temperature. If the temperature risesabove a preselected value, the current is reduced until the temperaturedrops below this value. This method has reduced the number of impedancerises during cardiac ablations but has not significantly increasedlesion dimensions. The results are not significantly different becausethis method still relies on the cooling effect of the blood which isdependent on location in the heart and orientation of the catheter toendocardial surface.

Another method is to irrigate the ablation electrode, e.g., withphysiologic saline at room temperature, to actively cool the ablationelectrode instead of relying on the more passive physiological coolingof the blood. Because the strength of the RF current is no longerlimited by the interface temperature, current can be increased. Thisresults in lesions which tend to be larger and more spherical, usuallymeasuring about 10 to 12 mm.

The clinical effectiveness of irrigating the ablation electrode isdependent upon the distribution of flow within the electrode structureand the rate of irrigation flow through the tip. Effectiveness isachieved by reducing the overall electrode temperature and eliminatinghot spots in the ablation electrode which can initiate coagulumformation. More channels and higher flows are more effective in reducingoverall temperature and temperature variations, i.e., hot spots. Thecoolant flow rate must be balanced against the amount of fluid that canbe injected into a patient and the increased clinical load required tomonitor and possibly refill the injection devices during a procedure. Inaddition to irrigation flow during ablation, a maintenance flow,typically at a lower flow rate, is required throughout the procedure toprevent backflow of blood flow into the coolant passages. Thus reducingcoolant flow by utilizing it as efficiently as possible is a desirabledesign objective.

In view of the foregoing, accurate and real-time temperature measurementat a catheter tip providing actual interfacial temperature is desirable.Typical temperature sensors for use with catheters can be up to 30degrees off from the actual tissue temperature. An ablation catheterwith improved temperature sensing capabilities should prevent thrombusformation and tissue charring. It would also provide better tissue/bloodcontact interface temperature reading allowing an operator better powercontrol. Improved temperature measurement would also have applicationsto other catheter-based technologies, such as esophagus, VT and otherapplications where tissue monitoring is a key measurement at a cathetertip.

For improved sensing capabilities, Micro-Electro-Mechanical Systems(MEMS) offer the integration of mechanical elements, sensors, actuators,and electronics on a common silicon substrate through microfabricationtechnology. MEMS components are typically made using microfabricationprocesses that can form very thin layers, and compatible“micromachining” processes that selectively etch away parts of a siliconwafer or add new structural layers to form mechanical andelectromechanical devices.

Sensor technology that can be integrated into semiconductor materialsfor sensing characteristics including temperature are well known in theart. A temperature gauge can be constructed using a resistor made of amaterial such as polysilicon, or other thermoresistive material, whoseresistance changes with temperature. Using this type of a sensor,temperature can be measured as a function of the change in theresistance of the material. Furthermore, a temperature gauge can also beconstructed by forming a thin film thermocouple.

In most if not all catheter-based ablation procedures, a challenge hasbeen to monitor the interfacial temperature of the catheter regardlessof the orientation of the catheter ablation tip. Because ablationcatheters are maneuvered to contact different surfaces at differentangles, a distal end reading and/or a circumferential reading of theinterfacial temperatures would be another advantage in avoid overheatingof tissue at the ablation site.

Accordingly, there exists a need for a catheter with improvedtemperature sensing capabilities, including an ablation catheter withmultiple microfabricated temperature sensors positioned on the outersurface of the distal end of the tip electrode and/or circumferentiallyon the outer surface of the tip section for real time, actualinterfacial temperature measurement.

SUMMARY OF THE INVENTION

In a more detailed embodiment of the catheter, each temperature sensorincludes a thin film assembly that is microfabricated and integrated onthe outer surface of the catheter tip section. Where the temperaturesensor is microfabricated on the flexible tubing of the tip section, acontact layer is deposited, following by the sensor layer, and followedby a protective layer. Where the temperature sensor is microfabricatedon the tip electrode, an insulating layer is deposited, followed by thecontact layer, followed by the sensor layer, and followed by theprotective layer. In another more detailed embodiment of the catheter,the catheter is adapted for irrigation and includes irrigation tubesegments that extend the catheter body and the tip section and lead toan outer surface of the tip electrode. In yet another more detailedembodiment, there are at least three circumferential sensor layersaround the tip section, each spanning between about 120 to 30 degrees,preferably about 90 to 45 degrees, more preferably about 60 degreesaround the tip section. There is also a tip sensor layer on the dome ordistal end of the tip electrode. The shape of each circumferentialsensor layer and/or the tip sensor layer may be generally rectangular.

Each sensor layer has a source lead wire and a return lead wire thatextend from the tip section through the catheter body to a controlhandle which may be manipulated to deflect the catheter. Holes areformed in the tip section, whether in the flexible tubing or the tipelectrode, to allow the lead wires to contact the sensor layer on theouter surface of the tip section. The lead wires allow a control systemto detect on a real time basis a change in the resistance of the sensorlayer to monitor interfacial temperature at or near the location of thesensor. The source lead wires and return lead wires are in signalcommunication with a control system to detect the interfacialtemperature at or near the location of each sensor by means of a changein resistance in each sensor layer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings, wherein:

FIG. 1 is an elevated side view of one embodiment of the catheteraccording to the present invention;

FIG. 2 is a side cross-sectional view of a catheter body according tothe catheter of FIG. 1, including the junction between the catheter bodyand the tip section;

FIG. 3A is a side cross-sectional view of an embodiment of a cathetertip section with circumferential temperature sensors on a flexibletubing taken along a first diameter;

FIG. 3B is a side cross-sectional view of another embodiment of acatheter tip section with circumferential temperature sensors on a tipelectrode taken along a first diameter;

FIG. 4A is a side cross-sectional view of the catheter tip section ofFIG. 3A taken along a second diameter generally perpendicular to thefirst diameter;

FIG. 4B is a side cross-sectional view of the catheter tip section ofFIG. 3B taken along a second diameter generally perpendicular to thefirst diameter;

FIG. 5A is a longitudinal cross-sectional view of the tip section ofFIG. 4A taken along line VA-VA;

FIG. 5B is a longitudinal cross-sectional view of the tip section ofFIG. 4A taken along line VB-VB.

FIG. 6 is a side cross-sectional view of a catheter tip section of FIG.3B taken along line VI-VI.

FIG. 7 is an end view of the tip section of FIGS. 3A and 3B;

FIG. 8 is a side view of an alternative embodiment of a catheter bodyaccording to the invention having a side arm for an infusion tube;

FIG. 9 is a schematic diagram of a system for controlling temperaturesensing electronics of the catheter;

FIG. 10 is a side cross-sectional view of an embodiment of a cathetercontrol handle according to the invention;

FIG. 11 is a side cross-sectional view of an embodiment of a temperaturesensor integrated on a flexible tubing of the catheter;

FIG. 12 is a side cross-sectional view of an alternative embodiment of atemperature sensor integrated on a catheter tip electrode; and

FIG. 13 is an embodiment of a sensor layer having a serpentine pattern.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a catheter with improved temperaturesensing capabilities. As shown in FIG. 1, a catheter 10 comprises anelongated catheter body 12 having proximal and distal ends, a tipsection 14 at the distal end of the catheter body 12 with temperaturesensors 52, and a control handle 16 at the proximal end of the catheterbody 12.

With reference to FIGS. 1 and 2, the catheter body 12 comprises anelongated tubular construction having a single, axial or central lumen18. The catheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A presentlypreferred construction comprises an outer wall 22 made of apolyurethane, or PEBAX. The outer wall 22 comprises an imbedded braidedmesh of stainless steel or the like to increase torsional stiffness ofthe catheter body 12 so that, when the control handle 16 is rotated, thetip section 14 of the catheter 10 will rotate in a corresponding manner.

Extending through the single lumen 18 of the catheter body 12 are leadwires, an infusion tube, and a compression coil through which a pullerwire 42 extends. A single lumen catheter body may be preferred withcertain applications over a multi-lumen body because it has been foundthat the single lumen body permits better tip control when rotating thecatheter. The single lumen permits the lead wires, infusion tube, andthe puller wire surrounded by the compression coil to float freelywithin the catheter body. If such wires and tube were restricted withinmultiple lumens, they tend to build up energy when the handle isrotated, resulting in the catheter body having a tendency to rotate backif, for example, the handle is released, or if bent around a curve, toflip over, either of which are undesirable performance characteristics.

The outer diameter of the catheter body 12 is not critical, but ispreferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 22 is not critical, but is thinenough so that the central lumen 18 can accommodate an infusion tube, apuller wire, lead wires, and any other wires, cables or tubes. The innersurface of the outer wall 22 is lined with a stiffening tube 20, whichcan be made of any suitable material, such as polyimide or nylon. Thestiffening tube 20, along with the braided outer wall 22, providesimproved torsional stability while at the same time minimizing the wallthickness of the catheter, thus maximizing the diameter of the centrallumen 18. The outer diameter of the stiffening tube 20 is about the sameas or slightly smaller than the inner diameter of the outer wall 22.Polyimide tubing is presently preferred for the stiffening tube 20because it may be very thin walled while still providing very goodstiffness. This maximizes the diameter of the central lumen 18 withoutsacrificing strength and stiffness.

An embodiment of a preferred catheter has an outer wall 22 with an outerdiameter of from about 0.090 inch to about 0.94 inch and an innerdiameter of from about 0.061 inch to about 0.065 inch and a polyimidestiffening tube 20 having an outer diameter of from about 0.060 inch toabout 0.064 inch and an inner diameter of from about 0.051 inch to about0.056 inch.

As shown in the embodiment of FIGS. 3A and 4A, the tip section 14comprises a short section of tubing 19 having multiple lumens, aconnecting section 9 of a single lumen tubing 11 distal the tubing 19,and a tip electrode 36 distal of the tubing 11. The tubings 11 and 19are made of a suitable non-toxic material that is preferably moreflexible than the catheter body 12. A presently preferred material forthe tubings 11 and 19 is braided polyurethane, i.e., polyurethane withan embedded mesh of braided stainless steel or the like. The outerdiameter of the tip section 14, like that of the catheter body 12, ispreferably no greater than about 8 french, more preferably 7 french. Thesize of the lumens is not critical. In an embodiment, the tubings 11 and19 each has an outer diameter of about 7 french (0.092 inch). Of thetubing 19, there are a first lumen 30, second lumen 32, a third lumen 34and a fourth lumen 35. The lumens 30, 32 and 34 are generally about thesame size, each having a diameter of from about 0.020 inch to about0.024 inch, preferably 0.022 inch. The fourth lumen 35 may have aslightly larger diameter of from about 0.032 inch to about 0.038 inch,preferably 0.036 inch. Of the tubing 11, there is a single lumen 13.

A means for attaching the catheter body 12 to the tip section 14 isillustrated in FIG. 2. The proximal end of the tip section 14 comprisesan outer circumferential notch 24 that receives the inner surface of theouter wall 22 of the catheter body 12. The tip section 14 and catheterbody 12 are attached by glue or the like. Before the tip section 14 andcatheter body 12 are attached, however, the stiffening tube 20 isinserted into the catheter body 12. The distal end of the stiffeningtube 20 is fixedly attached near the distal end of the catheter body 12by forming a glue joint 23 with polyurethane glue or the like.Preferably a small distance, e.g., about 3 mm, is provided between thedistal end of the catheter body 12 and the distal end of the stiffeningtube 20 to permit room for the catheter body 12 to receive the notch 24of the tip section 14. A force is applied to the proximal end of thestiffening tube 20, and, while the stiffening tube 20 is undercompression, a first glue joint (not shown) is made between thestiffening tube 20 and the outer wall 22 by a fast drying glue, e.g.Super Glue®. Thereafter a second glue joint 26 is formed between theproximal ends of the stiffening tube 20 and outer wall 22 using a slowerdrying but stronger glue, e.g., polyurethane.

If desired, a spacer can be located within the catheter body between thedistal end of the stiffening tube and the proximal end of the tipsection. The spacer provides a transition in flexibility at the junctionof the catheter body and tip section, which allows this junction to bendsmoothly without folding or kinking. A catheter having such a spacer isdescribed in U.S. patent application Ser. No. 08/924,616, entitled“Steerable Direct Myocardial Revascularization Catheter”, the disclosureof which is incorporated herein by reference.

A means for attaching the tip section 14 to the connecting section 9 isillustrated in FIGS. 3A and 4A. The distal end of the tubing 19comprises an outer circumferential notch 17 that receives a notchedinner surface 21 of the outer wall of the tubing 11. The tubings 19 and11 are attached by glue or the like.

At the distal end of the connecting section 9 is the tip electrode 36.The tip electrode 36 has a diameter about the same as the outer diameterof the tubing 19. As illustrated in the embodiment of FIGS. 3A and 4A,the tip electrode 36 is generally solid, having a fluid passage 45 and ablind hole 33 that corresponds in size and location to the lumen 34 inthe tip section 14. The blind hole 33 extends from the proximal end ofthe tip electrode 36, but does not extend through to the distal end ofthe tip electrode. It is understood that the configuration of the fluidpassage may vary as desired. Other suitable tip designs are disclosed inU.S. Pat. Nos. 6,602,242, 6,466,818, 6,405,078 and U.S. application Ser.No. 10/820,480 filed Apr. 2, 2004, the entire disclosures of which areincorporated herein by reference.

The tip electrode of FIGS. 3A and 4A has an effective length, i.e., fromits distal end to the distal end of the tubing, of about 3.5 mm, and anactual length, i.e., from its distal end to its proximal end, of about4.0 mm. As shown in FIGS. 3A and 4A, this tip electrode 36 is attachedto the tubing 9 by creating a notch 37 in the distal end of the tubing11 which receives a stem 31 formed in the proximal end of the tipelectrode 36, and filling the notch 37 with glue. The wires and tubesthat extend into the tip electrode 36 help to keep the tip electrode inplace on the tip section 14. The tip electrode 36 can be made of anysuitable material, and are preferably machined from platinum-iridium bar(90% platinum/10% iridium).

In accordance with the present invention, the catheter 10 of FIG. 1 hastip section 14 with a tip temperature sensor and multiplecircumferential or side temperature sensors on its outer surface. Asshown in FIG. 11, each circumferential temperature sensor 52 is amicrofabricated thin film assembly 54 that includes a thermoresistivesensor layer or film 56 that may be made of any suitable material, forexample, polysilicon, nickel, silicon, platinum and/or otherthermoresistive material. The thin film assembly 54 is directlydeposited onto a substrate 53, which in the embodiment of FIGS. 3A, 4Aand 5A is the outer wall of the tubing 11 of the section 9 In theembodiment of FIG. 11, the film assembly 54 includes a contact layer 55and a protecting coating 57, with the sensor layer 56 being depositedtherebetween.

The sensing layer 56 of the circumferential temperature sensor is a fewmillimeter in length along the catheter longitudinal axis rangingbetween about 5.0 mm and 0.1 mm, preferably about 3.0 mm and 1.5 mm, andmore preferably about 2.5 mm. The sensor layer 56 of the circumferentialtemperature sensor is a few millimeter in width ranging between about2.0 mm and 0.1 mm, preferably about 1.5 mm and 1.0 mm, and morepreferably about 1.2 mm. Each sensor layer 56 of the circumferentialtemperature sensor extends circumferentially around the section 9 andmay span between about 10 to 120 degrees, preferably about 45 to 90degrees, more preferably about 60 degrees around the tip section 14. Inthe illustrated embodiments, there are three circumferential temperaturesensor 52 b, 52 c and 52 d, each spanning about 60 degrees and separatedgenerally uniformly from each other by a distance of about 1.0 to 2.0mm. It is understood by one of ordinary skill in the art that there maybe a different plurality of circumferential temperature sensors, rangingbetween six and two, depending on factors including the plurality ofdistinct interfacial temperature readings desired and the size of thecatheter.

The illustrated embodiments of FIGS. 3 and 4 include a tip temperaturesensor 52 a integrated on the dome of the tip electrode 36. The tiptemperature sensor 52 a is a microfabricated thin film assembly 54′ thatincludes a thermoresistive sensor layer or film 56 that may be made ofany suitable material, for example, polysilicon, nickel, silicon,platinum and/or other thermoresistive material. The thin film assembly54′ is directly deposited onto substrate 53, which in this instance isthe tip electrode 36. As shown in FIG. 12, the assembly 54′ includes thecontact layer 55, the sensor layer 56, the protective coating 57, and aninsulating layer 58 that is deposited on the outer surface the tipelectrode 36 from the contact layer. The sensor layer of the tiptemperature sensor 52 a has a length ranging between about 5.0 mm and0.1 mm, preferably between about 3.0 mm and 1.0 mm, and more preferablybetween about 2.2 mm. The sensor layer of the tip temperature sensor 52a has a width ranging between about 1.0 mm and 0.1 mm, preferablybetween about 0.8 mm and 0.4 mm, and more preferably between about 0.6mm.

The sensor layer 56 of both the tip temperature sensor 52 a and thecircumferential temperature sensors 52 b-52 n is less than about 500nanometers in thickness, preferably ranging between 500 nm and 100 nmand more preferably about 300 nm and 100 nm. The sensor layer of the tiptemperature sensor 52 a and the sensor layers of the circumferentialtemperature sensors 52 b-52 n are separated by a distance of about 2.0to 3.0 mm.

The plurality and shape of the sensor layer 56 can be varied as desiredor appropriate. In the illustrated embodiments, sensor layers aregenerally rectangular. An alternative embodiment of the sensor layer isa serpentine pattern, that is, a configuration with at least two changesin direction (FIG. 13). In that regard, a serpentine pattern or apattern with a serpentine component can maximize the resistance of thesensor relative to contact resistances.

It is understood that each temperature sensor 52 can serve as a locationfor measuring temperature. With multiple sensors or sensors layers on atip section, the catheter can more easily detect location of hot spotsregardless of orientation of the tip electrode with respect to thetissue being ablated. The temperature sensor 52 is able to measuretemperature at or near the distal tip of the catheter. The sensor can beused to monitor tissue temperature and/or catheter tip temperatureduring treatment of atrial fibrillation symptoms, especially at thetissue-tip interface where most ablation occurs. Thus, the catheter 10of the present invention provides advantages that include the ability tomeasure not merely a single relative environmental temperature aroundthe tip of the catheter 10 but multiple interfacial temperature at thecatheter tip, and doing so on a real time basis with minimal time delaydue to small thermal mass of the sensors. In the area ofelectrophysiology, there are concerns with tissue overheating that arebetter managed and addressed by the catheter of the present invention.The catheter 10 provides an operator with an improved monitoring ofvarious interfacial temperatures to minimize the risks of coagulationand charring of the tissue or other damage to tissue due to overheating.

Referring back to FIGS. 3A, 4A and 6, the tip electrode 36 is connectedto a lead wire 40. Each sensor 52 is connected to its source lead wire41 s and return lead wire 41 r. The lead wires 40 and 41 r extendthrough the central lumen 13 of the tubing 9, the first lumen 30 oftubing 19, the central lumen 18 of the catheter body 12, and the controlhandle 16, and terminate at their proximal end in an input jack (notshown) that may be plugged into an appropriate monitor (not shown)and/or temperature sensing system (FIG. 9). The portion of the leadwires 40 and 41 r extending through the central lumen 18 of the catheterbody 12, control handle 16 and proximal end of the tip section 14 areenclosed within a protective sheath 39 r, which can be made of anysuitable material, preferably polyimide. The protective sheath 39 r isanchored at its distal end to the proximal end of the tip section 14 bygluing it in the lumen 30 with polyurethane glue or the like. The leadwires 40 and 41 r extend through the central lumen 13 of the tubing 9,the first lumen 30 of tubing 19, the central lumen 18 of the catheterbody 12, and the control handle 16, and terminate at their proximal endin an input jack (not shown) that may be plugged into an appropriatemonitor (not shown) and/or temperature sensing system (FIG. 9). Theportion of the lead wires 40 and 41 r extending through the centrallumen 18 of the catheter body 12, control handle 16 and proximal end ofthe tip section 14 are enclosed within a protective sheath 39 r, whichcan be made of any suitable material, preferably polyimide. Theprotective sheath 39 r is anchored at its distal end to the proximal endof the tip section 14 by gluing it in the lumen 30 with polyurethaneglue or the like.

The lead wires 41 s extend through the central lumen 13 of the tubing 9,the third lumen 34 of tubing 19, the central lumen 18 of the catheterbody 12, and the control handle 16, and terminate at their proximal endin an input jack (not shown) that may be plugged into an appropriatemonitor (not shown) and/or temperature sensing system (FIG. 9). Theportion of the lead wires 41 s extending through the central lumen 18 ofthe catheter body 12, control handle 16 and proximal end of the tipsection 14 are enclosed within a protective sheath 39 s, which can bemade of any suitable material, preferably polyimide. The protectivesheath 39 s is anchored at its distal end to the proximal end of the tipsection 14 by gluing it in the lumen 34 with polyurethane glue or thelike.

Connection of the lead wire 40 to the tip electrode 36 is accomplished,for example, by welding the lead wire 40 into the hole 33 in the tipelectrode. Connection of the lead wires 41 for the sensors 52 may beaccomplished by first making a small hole 43 through the substrate,e.g., tubing 11 for the circumferential sensors 52 b-52 n and the tipelectrode 36 for the tip sensor 52 a. Such a hole can be created in thetubing 11, for example, by inserting a needle through the tubing 19 andheating the needle sufficiently to form a permanent hole. Such a holecan be created in the tip electrode by drilling and/or etching. A leadwire 41 is then drawn through the hole by using a microhook or the like.The end of the lead wire 41 is then stripped of any coating and preparedand treated for connection to the sensor layer 56 as described furtherbelow.

An alternative embodiment of the catheter 10 is illustrated in FIGS. 3B,4B and 5C, an extended tip electrode 36′ is connected to the distal endof the tubing 19 of the section 14. The tip electrode 36′ has aneffective length, i.e., from its distal end to the distal end of thetubing, of about 7.5 mm, and an actual length, i.e., from its distal endto its proximal end, of about 8.0 mm. The tip electrode 36′ has adiameter about the same as the outer diameter of the tubing 19 and anopen longitudinal core 61 surrounded by a shell 63. The proximal end ofthe core 61 is in communication with the lumens of the tubing 19. Thedistal end of the core is proximal of the distal end of the tipelectrode 36′ and the core is in communication with a fluid passage 35′.An irrigation tube 89′ extends from the distal end of the tubing 19through the core 61 with its distal end in communication with thepassage 35. The tip electrode 36′ may be formed from a cylindrical rodwhose distal end is milled to form an atraumatic conical shape. The rodis then drilled from the proximal end, for example, with a drill bit ofa diameter D along the longitudinal axis to form the core. The fluidpassage 35′ is then formed by drilling from outer surface of the tipelectrode 36′ toward the core. It is understood that the fluid passageand/or branches thereof may vary as desired. A method of manufacturing asuitable tip electrode is described in U.S. patent application Ser. No.11/058,434, filed Feb. 14, 2005, entitled Irrigated Tip Catheter andMethod of Manufacturing Therefor, the entire disclosure of which ishereby incorporated by reference.

A blind hole 33′ is formed in the distal end of the core. The blind hole33 extends from the distal end of the core but does not extend throughto the distal end of the tip electrode. The distal end of a lead wire 40for the tip electrode 36′ is received and, for example, welded in theblind hole 33′.

In the embodiment of FIGS. 3B, 4B and 5B, the substrate 53 onto whichthe microfabricated thin film assembly 54′ of each of the tiptemperature sensor 52 a and the circumferential temperature sensors 52b-52 n is directly deposited is the shell 63 of the tip electrode 36′.As such, reference is again made to FIG. 12 which illustrates the filmassembly 54′ as including the contact layer 55, the sensor layer 56, theprotective coating 57, and an insulating layer 58 that is deposited onthe outer surface 65 of the shell 63 to insulate the tip electrode 36′from the contact layer. In that regard, it is understood by one ofordinary skill in the art that the embodiment of the film assembly 54 ofFIG. 11 may be better suited for nonconducting substrates (includingnon-metal tip electrodes) because without the insulating layer 58 sensorlayer signal will tend to flow through the substrate. As such, theembodiment of the film assembly 54′ of FIG. 12 may be better suited forconducting substrates. As understood by one of ordinary skill in theart, any of the layers shown in FIG. 11 or 12 can be omitted or appliedmultiple times as appropriate or desired.

Connection of the lead wires 41 for the sensors 52 may be accomplishedby first making a small hole 43′ through the shell 63 of the tipelectrode 36′. Such a hole can be created by any suitable process, forexample, by drilling or etching. A lead wire 41 is then drawn throughthe hole by using a microhook or the like. The end of the lead wire 41is then stripped of any coating and prepared and treated for connectionto the sensor layer 56 as described further below.

The thermistor sensor layer 56 of the sensors 52 acts like a thermallysensitive resistor in that it exhibits a change in electrical resistancewith a change in its temperature as reflective of the temperature of thetissue and/or fluid with which it is in contact. In one embodiment, theresistance is generally measured by passing a relatively small, measureddirect current through the film and measuring the voltage drop. As such,FIG. 9 shows a connection schematic for the catheter 10. An embodimentof a system S to control temperature sensing electronics of the catheter10 includes a stable constant voltage power supply 60 connected viaconnectors 62 to an amplified balanced sensing circuit 64 which sends toand receives signals from the sensor 52 via connector 66 and connector68, respectively. The sensing circuit 64 outputs signals to a low passfilter 70 via connector 72 and to a digital voltmeter 74 via connector76. The sensing circuit 64 also outputs signals directly to the digitalvoltmeter 74 via connector 78. An input power supply 80 supplies powerto the sensing circuit 64 via connector 82.

In use, a generally steady DC current is passed through the sensor 52 sas supplied by the battery bank 60 to the sensing circuit 64 whichdelivers the current via connector 66. The current output from thesensors 52 are passed back to the sensing circuit 64 via connector 68.The sensing circuit may include conventional logic circuitry for signalconditioning and/or multiplexing particularly where the catheter hasmore than one sensor 52. The current passes to a low pass filter 70 viaconnector 72 and to a digital voltmeter 74 via connector 76 beforeclosing the circuit loop with the sensing circuit 64 via connector 78.The voltmeter 74 measures voltage drop that results from a change inresistance of the sensors 52 that results from a change in thetemperature of its sensor layer 56. Accordingly, an operator of thecatheter can monitor the voltmeter for changes in the interfacialtemperatures at different locations, including at the distal end of thetip electrode and circumferential locations proximal of the distal end,to avoid coagulation and charring of tissue at the ablation treatmentsite, or any other damage from overheating the tissue.

The catheter is deflectable by means of a puller wire 42 that extendsthrough the catheter body 12. The puller wire 42 is anchored at itsproximal end to the control handle 16 (FIG. 8), and is anchored at itsdistal end to the tip section 14 (FIGS. 3A and 3B). The puller wire 42is made of any suitable metal, such as stainless steel or Nitinol, andis preferably coated with Teflon® or the like. The coating impartslubricity to the puller wire 42. The puller wire 42 preferably has adiameter ranging from about 0.006 to about 0.010 inches.

A compression coil 44, shown in FIG. 2, is situated within the catheterbody 12 in surrounding relation to the puller wire 42. The compressioncoil 44 extends from the proximal end of the catheter body 12 to theproximal end of the tip section 14. The compression coil 44 is made ofany suitable metal, preferably stainless steel. The compression coil 44is tightly wound on itself to provide flexibility, i.e., bending, but toresist compression. The inner diameter of the compression coil 44 ispreferably slightly larger than the diameter of the puller wire 42. TheTeflon® coating on the puller wire 42 allows it to slide freely withinthe compression coil 44. If desired, particularly if the lead wires 40are not enclosed by a protective sheath 39, the outer surface of thecompression coil 44 can be covered by a flexible, non-conductive sheath,e.g., made of polyimide tubing, to prevent contact between thecompression coil 44 and any other wires within the catheter body 12.

The compression coil 44 is anchored at its proximal end to the proximalend of the stiffening tube 20 in the catheter body 12 by glue joint 50and at its distal end to the tip section 14 by glue joint 51. Both gluejoints 50 and 51 preferably comprise polyurethane glue or the like. Theglue may be applied by means of a syringe or the like through a holemade between the outer surface of the catheter body 12 and the centrallumen 18. Such a hole may be formed, for example, by a needle or thelike that punctures the outer wall 22 of the catheter body 12 and thestiffening tube 20 which is heated sufficiently to form a permanenthole. The glue is then introduced through the hole to the outer surfaceof the compression coil 44 and wicks around the outer circumference toform a glue joint about the entire circumference of the compression coil44.

The puller wire 42 extends into the second lumen 32 of the tubing 19. Inthe embodiment of FIG. 3A, the puller wire 42 is anchored at its distalend to distal end of the lumen 32. A preferred method for anchoring thepuller wire 42 within the tip electrode 36 is by crimping metal tubing46 to the distal end of the puller wire 42 and gluing tubing 46 to thelumen 32. Alternatively, in the embodiment of FIG. 3B, the puller wire42 can be anchored in the distal end of the lumen 32 by a T-anchor 53fastened to the outer wall of the tubing 19. In any case, within thesecond lumen 32 of the tip section 14, the puller wire 42 extendsthrough a plastic, preferably Teflon®, sheath 81, which prevents thepuller wire 42 from cutting into the wall of the tip section 14 when thetip section is deflected. Longitudinal movement of the puller wire 42relative to the catheter body 12 which results in deflection of the tipsection, is accomplished by suitable manipulation of the control handle16. To that end, the control handle and the mechanisms therein can bevaried as desired.

An infusion tube is provided within the catheter body 12 for infusingfluids, e.g., saline, to cool the tip electrode. The infusion tube mayalso be used to infuse drugs or to collect tissue or fluid samples. Theinfusion tube may be made of any suitable material, and is preferablymade of polyimide tubing. A preferred infusion tube has an outerdiameter of from about 0.32 inch to about 0.036 inch and an innerdiameter of from about 0.28 inch to about 0.032 inch.

With reference to FIGS. 1, 2 and 5, a first infusion tube segment 88extends through the central lumen 18 of the catheter body 12 andterminates in the proximal end of the fourth lumen 35 of the tip section14. The distal end of the first infusion tube segment 88 is anchored inthe lumen 35 by polyurethane glue or the like. The proximal end of thefirst infusion tube segment 88 extends through the control handle 16 andterminates in a luer hub 90 or the like at a location proximal to thecontrol handle. A second infusion tube segment 89 is provided at thedistal end of the lumen 35 and extends into the fluid passage 45 of thetip electrode. The second infusion tube segment 89 is anchored withinthe lumen 35 and the fluid passage 45 by polyurethane glue or the like.The second infusion tube segment 89 like the puller wire 42, providesadditional support for the tip electrode. In practice, fluid may beinjected into the first infusion tube segment 88 through the luer hub90, and flows through the first infusion tube segment 88, through thethird lumen 35, through the second infusion tube segment, into 89 intothe fluid passage 45 in the tip electrode, and out the fluid passage 45in the tip electrode. Again, the fluid passage may have otherconfigurations as desired. In the illustrated embodiments, the fluidpassage 45 forms a longitudinal hole that extends out the distal end ofthe tip electrode, or the tip electrode 36 may be porous enough to allowfluids to pass to the outer surface of the tip electrode, theinterconnecting pores forming the fluid passage.

In an alternative arrangement, as shown in FIG. 8, a single lumen sidearm 94 is fluidly connected to the central lumen 18 near the proximalend of the catheter body 12. The first infusion tube segment 88 extendsthrough the catheter body 12 and out the side arm 94, where itterminates in a luer hub 90 or the like. The side arm 94 is preferablymade of the same material as the outer wall 22, but preferably has agreater thickness, e.g., 0.055 inch. Where the side arm 94 meets thecatheter body 12, a molded joint can be provided to provide additionalstrength and support The molded joint can be made of any suitablebiocompatable material, and is preferably made of polyurethane.

FIGS. 11 and 12 illustrate methods for the microfabrication of thesensor 52 directly on to the substrate 53, which, as mentioned, can beeither the tubing 11 of the connecting section 9 or the shell 63 of thetip electrode 36, 36′. A plurality of cavities such as pockets 47, holes43 and slots may be formed in a selected surface of the substrate ontowhich the sensor 52 is deposited. These can be accomplished bytechniques known in the art such as mechanical drilling, boring, laserablation, EDM, and photochemical etching. Depositions of sensor layermaterial such as nickel, silicon, polysilicon, platinum and/or otherthermoresistive material are realized by various physical and/orchemical deposition techniques known in the art. These include, forexample, spin casting, casting, stamping, molding, sputtering, thermalevaporation, PECVD, LPCVD, electroplating, electroless plating, andsol-gel. The same deposition techniques may be used for creating theinsulation coating 58 between metal substrates (e.g., the tip electrode36′) and the sensor layer 56, if appropriate. For example, a thininsulation coating such as parylene may be deposited. The protectivecoating 57 may also be applied over the sensor layer 56 to protect itfrom elements, such as blood.

Below is a table showing a method of fabricating the sensor in a smallbatch process:

Action Sub-Action Base Layer Preparation Evaporation Post-InspectionContact Layer Sensor Layer Preparation Sputtering Post-InspectionEncapsulation Layer Preparation Evaporation Post-Inspection

Below is a table showing a method of fabricating the sensor in a largebatch process:

Action Sub-Action Substrate Surface Chemical clean/etc. CleaningBase/Insulation Preparation Layer Evaporation Post-Inspection LaserProcessing Preparation Laser Processing Post-Inspection Contact LayerPreparation Deposition Post-Inspection Sensor Layer PreparationSputtering Post-Inspection Encapsulation Layer Preparation EvaporationPost-Inspection

Suitable detailed manufacturing processes of the sensor 52, the thinfilm assembly 54 and the sensor layer 56 are described in U.S. PatentApplication “Medical and Surgical Devices with Integrated Sensors”, No.PCT/US04/02547, filed in Jan. 30, 2004, which claims priority of U.S.Provisional Patent Application No. 60/443,877 (Jan. 31, 2003), theentire disclosures of both of which are incorporated herein byreference.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate that theFigures are not necessarily to scale and alterations and changes in thedescribed structure may be practiced without meaningfully departing fromthe principal spirit and scope of this invention. Accordingly, theforegoing description should not be read as pertaining only to theprecise structures described and illustrated in the accompanyingdrawings, but rather should be read consistent with and as support forthe following claims which are to have their fullest and fairest scope.

What is claimed is:
 1. A catheter comprising: a catheter body havingproximal and distal ends; a tip section at the distal end of thecatheter body, the tip section comprising a plurality of temperaturesensors on an outer surface of the tip section, wherein each of thetemperature sensors comprises a contact layer and a thin film sensorlayer, the thin film sensor layer having a film thickness of about 500nm or less, the tip section further comprising at its distal end a tipelectrode, wherein the plurality of temperature sensors comprises: atleast one tip temperature sensor on at least a portion of an outersurface of a distal-most tip end of the tip electrode, and at least onecircumferential temperature sensor extending circumferentially about 10to 120 degrees around the outer surface of the tip section, wherein afirst circumferential temperature sensor is on an outer circumferentialsurface of the tip electrode, wherein the contact layer of the at leastone tip temperature sensor is embedded in the outer surface of thedistal-most tip end of the tip electrode, and the thin film sensor layerof the at least one tip temperature sensor is on the contact layer andthe outer surface of the distal-most tip end of the tip electrode.
 2. Acatheter of claim 1, wherein the tip section comprises a section oftubing proximal of the tip electrode and a second circumferentialtemperature sensor is on an outer surface of the tubing.
 3. A catheterof claim 1, wherein the sensor layer comprises a thin filmthermoresistive material.
 4. A catheter of claim 1, wherein the sensorlayer has a resistance that changes with changes in temperature.
 5. Acatheter of claim 1, wherein the first circumferential temperaturesensor on the outer circumferential surface of the tip electrodecomprises a nonconducting layer.
 6. A catheter of claim 5, wherein thenonconducting layer comprises a protective layer.
 7. A catheter of claim5, wherein the nonconducting layer comprises an insulating layer.
 8. Acatheter of claim 5, wherein the nonconducting layer comprises amaterial selected from the group consisting of parylene, polyimide andcombinations thereof.
 9. A catheter of claim 1, wherein at least one ofthe sensors comprises a protective layer.
 10. A catheter of claim 1,wherein the sensor layer comprises a material selected from the groupconsisting of nickel, platinum, silicon and polysilicon.
 11. A catheterof claim 1, wherein the sensor layer is generally rectangular.
 12. Acatheter of claim 1, wherein the sensor layer has a configurationincluding a serpentine pattern.
 13. A catheter of claim 1, wherein thesensor layer is lithographically patterned onto the outer surface of thetip section.
 14. A catheter of claim 13, wherein the deflecting meanscomprises a puller wire having a proximal end and a distal end, thepuller wire extending from a control handle, through the catheter bodyand into a lumen in the tip section, wherein the distal end of thepuller wire is fixedly secured within the tip section and the proximalend of the puller wire is fixedly secured in the control handle, wherebymanipulation of the control handle moves the puller wire relative to thecatheter body, resulting in deflection of the tip section.
 15. Acatheter of claim 1, wherein the catheter is adapted for ablation.
 16. Acatheter of claim 1, further comprising a control handle at the proximalend of the catheter body.
 17. A catheter of claim 16, further comprisingmeans for deflecting the tip section by manipulation of the controlhandle.
 18. A catheter of claim 1, wherein the tip electrode has atleast one fluid passage in fluid communication with a lumen in the tipsection, and the catheter comprises an infusion tube having proximal anddistal ends, said infusion tube extending through a central lumen in thecatheter body and through a lumen in the tip section, and being anchoredat its distal end in a proximal end of the fluid passage in the tipelectrode, whereby fluid can flow through the infusion tube, into thefluid passage in the tip electrode and through the tip electrode to theouter surface of the tip electrode.
 19. A catheter according to claim 1,wherein the tip section has three lumens extending therethrough.
 20. Acatheter according to claim 1 further comprising deflecting means.
 21. Acatheter of claim 1, wherein the catheter is adapted for use with atemperature monitoring system comprising: a DC power source supplying agenerally steady DC current to pass through the plurality of temperaturesensors; a sensing circuit connected to the temperature sensors to passsaid current; a voltmeter to measure a change in voltage resulting froma change in resistance of the temperature sensors.
 22. A cathetercomprising: an elongated flexible tubular catheter body having proximaland distal ends; a tip section at the distal end of the catheter body,the tip section comprising a tubing section and a tip electrode at adistal end of the tubing section, wherein the tip section has on itsouter surface a plurality of integrated microfabricated temperaturesensors, each temperature sensor comprising a contact layer and a sensorlayer, the sensor layer having a thickness of about 500 nm or less,wherein the plurality of temperature sensors comprises: at least one tiptemperature sensor on at least a portion of an outer surface of adistal-most tip end of the tip electrode, and at least onecircumferential temperature sensor extending circumferentially about 45to 90 degrees around the outer surface of the tip section, wherein afirst temperature sensor is on an outer surface of the tip electrode,wherein the contact layer of the at least one tip temperature sensor isembedded in the outer surface of the distal-most tip end of the tipelectrode, and the sensor layer of the at least one tip temperaturesensor is on the contact layer and the outer surface of the distal-mosttip end of the tip electrode.
 23. A catheter of claim 22, wherein atleast a second circumferential temperature sensor is integrated on anouter surface of the tubing section.
 24. A catheter of claim 22, whereineach sensor comprises a thin film thermoresistive material.
 25. Acatheter of claim 22, wherein each sensor has a resistance that changeswith changes in temperature.
 26. A catheter of claim 22, wherein eachsensor comprises a nonconducting layer.
 27. A catheter of claim 26,wherein the nonconducting layer comprises a protective layer.
 28. Acatheter of claim 26, wherein the nonconducting layer comprises aninsulating layer.
 29. A catheter of claim 26, wherein the nonconductinglayer comprises a material selected from the group consisting ofparylene, polyimide and combinations thereof.
 30. A catheter of claim22, wherein each sensor further comprises a protective layer.
 31. Acatheter of claim 22, wherein the sensor layer comprises a materialselected from the group consisting of nickel, platinum, silicon,polysilicon, and combinations thereof.
 32. A catheter comprising: anelongated flexible tubular catheter body having proximal and distalends; a tip section at the distal end of the catheter body, the tipsection comprising a tubing section and a tip electrode at a distal endof the tubing section, wherein the tip section has on its outer surfaceat least one integrated microfabricated circumferential temperaturesensor extending circumferentially about 60 degrees around the outersurface of the tip section, a first circumferential temperature sensorbeing on an outer circumferential surface of the tip electrode, and thetip electrode has on at least a portion of an outer surface of itsdistal-most tip end an integrated microfabricated tip temperaturesensor, wherein each of the microfabricated tip temperature sensor andthe integrated microfabricated circumferential temperature sensorcomprises a contact layer and a sensor layer, the sensor layer having athickness of about 500 nm or less, wherein the contact layer of the tiptemperature sensor is embedded in the outer surface of the distal-mosttip end of the tip electrode, and the sensor layer of the tiptemperature sensor is on the contact layer and the outer surface of thedistal-most tip end of the tip electrode.